Ignition system



- March 2, 1948. s o 2,436,905 IGNITION SYSTEM Filed May 14, 1946 INVENTOR Patented Mar. 2, 1 948 a'c-rr. a

2,436,905 IGNITION srs'rini Brooks H. Short, Anderson, Ind., 'assignor to r "General Motors CorporationyDetr-oit, Mich., a v corporation oiDelawarc j r (A plication Mayi i, 194e, seriaino. 669,497".

'- 3 Claims. (01. 315 -210) QN TED,sTATEs PA'TYENTQOFFICE'I 1 This invention relates to ahigh frequency igniminal 26 of timer T. Terminal 26 is connected tion system'for an internal combustion engine by leaf spring 21 with a circuit breaker lever 28 and, more particularly, to a' system having a pivoted at 29 on a breaker plate 30 and having resonator at'each spark plug, the resonators of a non-conducting rubbing block 3| for engaging the'different spark'plugs being tuned to different a timer cam 32. Lever 28 carries a contact 33 frequencies, an oscillator having a'variable com for making engagement with a contact 34. An denser which can be adjusted to tune the oscilauxiliary condenser 35, preferably .001 mf., is lator successively with the various resonators at connected between wire 2| and the wire connectthe spark plugs, a'timer for controlling the 'opering resistance 25 with terminal 26.

ation of the oscillator and mechanically con- Timer contact 34 is connected through resistnected with its variable condenser whereby igniance 36,preferably 2500 ohms, which'is connected tion is provided at the engine'spark' plugs in by resistance element 31, preferably 25,000'ohms, recurrent sequence. "The system referred to is connected with wire 2|. Resistances 36 and 31 disclosed in-my copending application, Serial No. are connected with the grid 39 of thyratron 40 606,645; filed July 13;'1945,' which discloses the 1 whose cathode 4| is connected with wire 2|. Wire supply of energy to the'oscillator through'a thy- 38,'leading from power pack low voltage terminal ratron tubewhichis'caused to be conducting by I3, is connected with cathode heater 42 connected the closing of the contacts of the timer. with resistance 43 which is grounded. Thyratron An object of the present invention is to provide plate 44 is connected with Wire 38 which is cona system of the type referred toin which the nected'with cathode 46 of oscillator tube 45. The energy for operating the oscillator is supplied by terminals of cathode 46 are connected with a discharging a condenser. In the disclosed emcondenser 46a. The plate 41 of oscillator tube 45 bodiment of the invention, main and auxiliary is connected by wire 48 with high frequency choke condensers are charged by a power source, and 49 which is connected with 'the wire I9. The closing of the timer contacts causes the auxiliary grid 50 of oscillator tube 45 is connected by wire condenser to discharge through the grid of the 51 with condenser 53 and grid resistance 52 conthyratron to render it conducting whereupon the nected in parallel and both together with a wire main condenser discharges through the oscillator 56 connected with primary 55 of oscillator coil to the thyratron, thethyratron becoming non- 54. The primary 55 comprises sections 55a and conducting when the main condenser is com- 55b connected with a tap 550 which is grounded. pletely discharged whereupon the main condenser Wire 51 connects primary section 551) with a conis recharged while the auxiliary condenser redenser 58 connected with wire 48. Between Wires mains uncharged until after the timer contacts 56 and 51, there is connected the terminals of a open. variable condenser 85, the movable plates of which Further objects and advantages of the present re turned by a sh 3 connected h h i niinvention will be apparent from the following tion timer cam 32. An adjustable core 59 extends description, reference being had to the accomwithin p m y 0 1 panying drawing, wherein a preferred embodisso d Wi h e p y is a ec y ment of the present invention is clearly shown. winding 60 of a few turns in which is induced a The figure of the drawing is a wiring diagram high fr q e cy Current O 10W Voltage high of an embodiment of the present invention. amperag The second ry 60 is connected in Referring to the drawing, a storage battery In s i s with pr ary coils 63 and 6 o grounded at I I is connected by a switch I z with resonators 65, 66, 61 and 68, respectiv ly, h vin the low voltage terminal I3 of a power pack 15 secondary windings l ,1 and r p ively, whose other low voltage terminal I4 is grounded. c nn t wi h sp rk ap f p rk pl s 15. The high voltage terminals I6 and I! of the power 71 a d espe t e y, and each with a conpack are connected by a main condenser 20 prefdenser 80; The natural frequencies of the reserably one microfarad and a resistance I8prefonators are substantially different and are detererably 250 ohms. Condenser 20 is connected by m e by o s 3| W c an be so adjusted wires I9 and 2| with voltage divider resistances as to pr difierentdistences Withinithe I 22 and 23 having a tap at 24. I The element 22 ondary windings of the resonators.

has preferably .5 megohm resistance and the When switch I2 is closed current is supplied element 23 has 5 megohms resistance. The tap from the battery for heating the cathode 46 of 24 is connected with resistance element 25, prefoscillator tube and for heating the cathode erably .75 megohm, which is connected with terheater 42 of thyratronfifl, and the power pack 15 operates to produce high voltage across its terminals l6 and I1 for the purpose of charging the main condenser 20 at a high voltage and the auxiliary condenser 35 at a lower voltage. When the timer contacts close, condenser 35 discharges through the grid 39 of thyratron 40, causing the latter to become conducting whereupon the main condenser 20 discharges through the thyratron 40 and the oscillator 45 through the following circuit: Wire 2 I, cathode 4 I, plate 44 of thyratron 40, wire 38., cathode 46 and plate 41 of oscillator tube 45, wire 48, choke 49, wire l9. Condenser 20 supplies energy to the oscillator during the discharge period. When condenser 20 is completely discharged, the thyratron 40 becomes nonconducting and allows condensers 20 and 35 to recharge. However, the condenser 35 cannot be recharged until after the contact 33 separates from the contact 34.

As stated before, the instant the contact 33 engages contact 34, condenser 35 discharge and thyratron 40 becomes conducting, thereby impressing a high voltage upon the plate 41 of tube 45. Tube 45 then. becomes conducting and condenser Zli discharges through it. During this discharge, high frequency oscillations are produced in the oscillator primary coil 55. In the secondary 6|) of relatively few turns, there is induced a high frequency current of low voltage and high amperage. The frequency of the oscillator is determined by the adjustment or posi tion of the movable plates of the condenser 85 which is driven by the engine concurrently with the timer cam 32. When the time arrives for the firing of a certain engine cylinder, the timer contacts close. and at that instant the movable plates of the variable condenser 85 are so positioned that the oscillator 54 is tuned only to the resonator associated with that spark plug which is in the cylinder to be fired. For that reason, a spark of high voltage and frequency will occur only at the gap of that spark plug. Sparking does not occur at the other gaps of the resonators not in tune with the oscillator at the time of discharge of coil 54 because the resonator which is in tune with the oscillator receives a very large portion of the total wattage. Hence the resonators of the spark plugs not to be fired receive a voltage which is too low to jump the spark gap.

Whenever a sufficient voltage is impressed on the plate 41. of .tube 45, the oscillator tube 45 permits current to flow to charge the condenser 85. The condenser charging circuit includes power pack terminal i1, wire I9, choke 49, condenser 58, condenser 85, resistance 52, wire grid 50, cathode 46, wire 38, plate 44, cathode 4|, wire 2| and power pack terminal l6. During the charge of condenser 85, the voltage imressed on the grid 50 becomes increasingly positive. As grid 50 becomes more positive, tube 45 passes more currentv and the voltage drop across the tube decreases. As the voltage drop decreases across tube 45, the condenser 85 starts discharging and produces a negative voltage on the grid 50 due to the operation of two inductively related circuits. One of these circuits is condenser 85, wire 51, all of the oscillator primary coil 55 and wire 56; and the other circuit includes the grounded tap 550 of primary 55, the primary section 55a, wire 56, resistance 52, wire 5|, grid 50, cathode 46 and ground connection back to 550. The negative voltage impressed on grid 50 causes less current to new from the plate 41, thereby raising the voltage drop across the tube 45 and allowing the condenser to be charged again. In this way, an oscillation through the primary 55 is sustained. This oscillation increases rapidly in amplitude until the maximum amplitude is reached; and the oscillation is sustained so long as sufiicient voltage is impressed on the plate 41 of oscillator tube 45. In other words, the oscillator tube 45 operates in a manner analogous to a variable resistance in shunt with the condenser 85. As condenser charge increases, the variable resistance decreases automatically; and, when the decrease of resistance is such that the condenser is robbed of charging current, the condenser discharges. The discharge of the condenser automatically causes the variable resistance to increase whereby the condenser is permitted to receive a charging current; and the cycle is repeated so long as sufiicient voltage is being impressed on the plate 41 of tube 45.

'As' the current oscillation through the oscillator primary coil 55 increases in magnitude that resonator with which the condenser 85 is tuned will have, in its condenser-coil circuit, a corresponding oscillation increasing in magnitude until voltage impressed upon the spark plug is sufficient to cause the current to jump the gap. As stated before, only the resonator which is in tune with the oscillator receives the benefit of the alternating charge and discharge of the condenser 85.

The present system is particularly useful for supplying ignition to high speed engines. Since the time intervals between sparking are relatively short, it is desirable to use as much as possible of the time interval to recondition the system for the next sparking operation. Therefore, as soon as the main condenser has discharged, it starts charging again without waiting for the timer contacts to open. The main condenser cannot discharge again until after the interval during which the contacts separate and reclose. Therefore, the charging time of the main condenser is the time between the beginning of successive ignitions less the time of main condenser discharge before the thyratron becomes non-conducting. This charging time includes all of the time during which the timer contacts are open and may include part of the time during which the contacts remain closed after the thyratron becomes non-conducting.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be 7 adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. An ignition system comprising a resonator connected with a spark gap, an oscillator including a coil inductively coupled with the resonator, a variable condenser for tuning the oscillator to the resonator and a tube, a power source, main and auxiliary condensers charged by the source, a thyratron through which the main condenser will discharge to the oscillator tube when the thyratron becomes conducting, and means for causing the auxiliary condenser to discharge to the grid of the thyratron to render it conducting.

2. An ignition system for a multicylinder engine comprising resonators respectively connected with the spark plugs of the engine, said resonators having different frequencies, an oscillator including a coil inductively coupled with the resonators, a variable condenser by which the oscillator can be tuned with the several resonators in recurrent sequence and an oscillator tube, a. power source, main and auxiliary condensers charged by the source, a thyratron through which the main condenser will discharge to the oscillator tube when the thyratron becomes conducting, a timer for causing the auxiliary condenser to discharge to the grid of the thyratron to render it conducting, and means for mechanically connecting the timer with the variable condenser.

3. An ignition system comprising a resonator connected with a spark gap, an oscillator including a coil inductively coupled with the resonator,

device to the oscillator tube, and a timer for causing the auxiliary condenser to discharge to said means.

BROOKS H. SHORT. 

